Polymeric materials

ABSTRACT

Apparatus for undertaking a chemical reaction includes an elongate housing and a receptacle. The elongate housing may include a cooling means, and end fittings, which may include ports where fluids may be introduced and/or removed. In use of the apparatus, a chemical reaction product is formed within the receptacle. Subsequently the receptacle containing the chemical reaction product is withdrawn from the elongate housing.

This invention relates to polymeric materials and particularly, although not exclusively, relates to apparatus for producing polymers, a method of producing polymers per se and related aspects thereof. Preferred embodiments relate to a drag reducing formulation which comprises the polymers and uses thereof in drag reduction e.g. to reduce the effect of friction (“drag”) experienced by a liquid hydrocarbon flowing through a hydrocarbon transportation pipeline.

The use of polymers and/or copolymers of alpha-olefins to reduce the effect of friction (“drag”) experienced by a liquid hydrocarbon flowing through a hydrocarbon transportation pipeline is well-known in the art. Reduction of the drag decreases the amount of energy needed to accomplish such flow, and therefore also decreases the costs associated with pumping. These materials, often called drag reducing agents (DRAs), can take various forms, including certain polymers in oil soluble suspensions, emulsions, pellets, gels, microfine powders and particulate slurries, for example comprising aqueous, organic or mixed aqueous/organic solvents. In some cases, the DRA may comprise a ‘true’ solution in an appropriate carrier solvent (e.g. dilute polymer solution product, produced in a solution polymerisation process). However, particulate slurries that comprise ground polymers are often the least expensive form.

The polymers that are most commonly used in preparing DRAs are poly(alpha-olefins) of carbon chain lengths ranging from 2 to about 40. Typically these polymers are prepared using Ziegler-Natta catalysts and frequently also co-catalysts such as alkyl aluminium compounds. These polymerization reactions tend to be very efficient, producing relatively high yield when carried out in bulk. However, they also tend to be highly exothermic. The exotherm itself creates problems which reduce the usefulness of the product if the exotherm is not effectively managed. These problems include, but are not necessarily limited to, a substantial reduction in the polymer molecular weight. This can substantially reduce the efficacy of the polymer in a drag reducing agent formulation.

Various different types of apparatus have been described for producing polymers and/or copolymers of alpha-olefins as described below.

U.S. Pat. Nos. 5,504,132 and 5,504,131 describe the preparation and use of non-crystalline high molecular weight hydrocarbon soluble drag reducing polymers. The documents describe suitable polymerization reaction vessels as being polymeric bottles and bags. It is stated the invention there described has been demonstrated with bottles and bags containing five to seven layers, including a water impervious polyolefin such as polypropylene, polyethylene, polybutylene, a bonding polymer, and ethylene vinyl alcohol copolymer oxygen barrier, another bonding polymer, and externally coated with polyethylene, polypropylene or polybutylene. Use of polyethylene terephthlate as an additional layer to add reactor strength at high temperatures is stated to be most preferred. One disadvantage of use of the bottle and bag described is that the produced poly(alpha-olefin) polymer is extremely adherent to the walls of the reactor vessels. As a result, the polymeric vessels cannot be separated from the poly(alpha-olefin) polymer. Instead, the bottles or bags are ground together with the polymer in forming the drag reducing material. This is, however, disadvantageous and undesirable—the material of the bottles or bag may contaminate downstream processes or products, for example within oil refineries. When contamination reaches the refined fuel, adverse effects such as filter blockages may occur in the end fuel application.

U.S. Pat. Nos. 7,534,403, 7,582,708, 8,105,547 and 8,110,150 describe polymerization reactors for creating drag-reducing polymers. The reactors are said to address the problem of removal of heat from the DRA polymerization reactor without the addition of cooling additives. The solution to the problem involves use of a reactor which includes a reservoir which incorporates an array of plates which define a heat exchanger. In one embodiment, seventeen, 4 feet heat exchanger plates are spaced apart by 4 13/16 inches. Disadvantageously, it is difficult using the apparatus to achieve consistent product quality, due to the dimensions and it may be difficult to separate the polymer from the heat exchanger plates.

U.S. Pat. No. 6,649,670B describes continuous polymerization and ambient grinding methods for polyolefin drag reducing agents. In one embodiment, there is described a continuous polymerization method which involves a “form, fill and seal” packaging process. Polymerization apparatus may comprise a continuous stirred tank reactor (CSTR) where raw materials (e.g. monomers. and catalysts) are continuously charged, allowed an appropriate dwell or residence time in the reactor system, such that adequate molecular weight or viscosity is sustained and, subsequently, discharged in a continuous fashion to a “form, fill and seal” packaging device. The packaging device may form bags which serve as temporary and isolated reactor vessels which are collected, kept in the presence of an inert atmosphere and reactants allowed to polymerise to high conversion.

U.S. Pat. No. 6,906,150 discloses a method of preparing polymers which are drag reducing agents. The method comprises allowing a polymerization mixture to polymerize in at least one closed reaction chamber configured as a linear void space with a linear axis and a cross-section and first and second ends, where the linear void space is surrounded by a chamber wall having an inner chamber surface and an outer heat exchange surface. Coolant is passed over the outer heat exchange surface to remove heat therefrom. The ends of the reaction chamber are opened and essentially all of the polymer is removed from each reaction chamber with a harvesting plunger. The harvesting plunger travels along the linear axis of the void space from the first end to the second end thereof. However, use of harvesting plungers is impractical as apparatus comprising such plungers is expensive to manufacture, the plungers are not very effective for removing the solid polymer from the reaction chambers and, furthermore, cleaning of the apparatus ready for recharging of the reaction chambers is time-consuming and difficult.

It is an object of the present invention to provide an apparatus for producing drag reducing polymers which may be advantageous.

It is an object of the present invention to provide a method of producing drag reducing polymers which may be advantageous.

According to a first aspect of the invention, there is provided an apparatus for undertaking a polymerisation reaction to produce a drag reducing polymer, the apparatus comprising:

(a) an elongate housing; and (b) an elongate receptacle within the housing, said receptacle being arranged to receive reagents for reaction in the apparatus to produce a drag reducing polymer.

In one embodiment, said elongate housing may comprise a rigid elongate support tube assembly 4 shown in FIG. 1 and the elongate receptacle may comprise an inflatable plastic reaction tube 12 shown in the same figure.

Said receptacle is preferably not self-supporting. It is preferably flaccid unless inflated or otherwise supported by external means as described herein.

Said receptacle preferably comprises a plastic material (eg a polymeric material), for example a plastic film material which has been arranged to define said receptacle. Said film material may have a thickness of at least 20 μm, suitably at least 50 μm, preferably at least 100 μm.

The thickness of the film material may be less than 2000 μm, preferably less than 1000 μm, more preferably less than 500 μm. The internal wall area of the receptacle may be defined as the area of the receptacle which is arranged to contain material (e.g. polymer in use). Suitably, at least 50%, preferably at least 75%, more preferably at least 90%, especially about 100% of the internal wall area is defined by a said plastic film material having a thickness in the range defined. The thickness of the film material may be between 20 μm and 1000 μm, preferably between 50 μm and 500 μm.

The internal wall area of the receptacle as described is preferably defined by a plastic film material which consists of a single layer. Thus, the receptacle preferably does not comprise a laminate and/or a multi-ply material. Said internal wall area of the receptacle preferably has a substantially smooth surface.

An external wall area of the receptacle, being the wall area of the receptacle on an opposite side of the film material to that of the internal wall area, preferably has a substantially smooth surface as described for that of the internal wall area. Said internal wall area and said external wall area preferably consist of identical materials and, preferably, represent opposing surfaces of the same material.

Preferably, substantially the entirety of said receptacle comprises said plastic material, more preferably said plastic film material as described.

As described, said receptacle preferably comprises a plastic material, for example a plastic film material. Suitably, at least 90 wt %, preferably at least 95 wt %, more preferably 100 wt % of said receptacle is made up of said plastic material.

Said plastic material is suitably sufficiently strong and inert to withstand the polymerisation reaction and not to adhere significantly to the polymer as it is forming. It is also preferably relatively cheap, so it can be discarded after use. Said plastic material is preferably heat sealable. It is preferably a thermoplastic polymer. It is preferably chemically compatible with the reagents used and polymer produced in the polymerisation reaction. Said plastic material preferably comprises optionally-substituted, preferably unsubstituted, alkylene (eg ethylene) repeat units which may be components of a homopolymer or copolymer. Said plastic material preferably comprises an optionally-substituted, preferably unsubstituted, polyolefin polymer, such as a polyalkylene polymer, for example polyethylene.

Said receptacle preferably includes a first end and a second end which are spaced apart along the elongate extent of the receptacle. Said first end is preferably a closed end and, more preferably, is substantially permanently closed—i.e. it is preferably not openable, except by, for example, destruction of the receptacle. Said first end preferably includes a sealed, for example a heat sealed region, suitably whereby opposing walls of the receptacle have been secured together, for example heat bonded together, thereby to define the closed end. The length of the receptacle is suitably the linear distance between said first end and said second end.

In the context of the present specification and unless the context otherwise requires, the diameter of the elongate receptacle refers to the longest straight line passing from one side of the cross-section of the receptacle to an opposite side, when the receptacle is in a distended (eg inflated) state and/or when it is configured to define its maximum cross-sectional area.

In the context of an elongate receptacle having a substantially symmetrical cross-sectional shape (eg having a substantially circular cross-section), the diameter of the elongate receptacle refers to a straight line passing from one side to an opposite side of the receptacle, through the centre of the cross-section, when the receptacle is in a distended (eg inflated) state and/or when it is configured to define its maximum cross-sectional area.

Preferably, the diameter of the receptacle is substantially constant for at least 80% (preferably at least 90% or 95%) of the length thereof. In a preferred embodiment, a region of the receptacle adjacent said second end diverges (or is suitably splayed) so an opening of the receptacle at said second end has a greater diameter than a region of the receptacle inwards of the second end. Such an arrangement facilitates securement and sealing of the second end in position in a way which minimises creation of air gaps in use.

The diameter of the receptacle may be in the range 1 cm to 45 cm across its entire extent. When the second end diverges as described, the maximum diameter of the divergent region may be up to 30% greater than the diameter of the receptacle upstream of the divergent region. The length of the receptacle may be in the range 15 cm to 60 m. The volume of the receptacle may be in the range 12 cm³ to 4 m³. Preferably, the diameter of the receptacle (suitably across at least 80% of the length of the receptacle) is less than 30 cm. It is more preferably less than 11 cm. It may be at least 7 cm. The length of the receptacle is preferably in the range 3 m to 15 m, especially in the range 4 m to 11 m. The volume of the receptacle is preferably in the range 4000 cm³ to 0.5 m³, for example in the range 10000 cm³ to 0.15 m³, more preferably in the range 20000 cm³ to 0.12 m³. The diameter, length and/or volume are suitably selected as described to optimise the polymerisation process and/or curing of polymer within the receptacle. It is found that if the diameter, length and/or volume are too great, there may be insufficient heat transfer during the polymerisation. This may mean that the degree of polymerisation across the diameter and/or within the volume may be unacceptably variable which may result in production of an inferior drag reducing polymer.

The aspect ratio of the elongate receptacle may be defined as the length of the internal volume of the receptacle divided by the diameter of the internal volume of the receptacle. Said aspect ratio may be at least 10, suitably at least 20, preferably at least 30. Said aspect ratio may be less than 600, preferably less than 300, more preferably less than 150. Said aspect ratio is preferably between 10 and 300, more preferably between 30 and 150.

Preferably, other than any means by which the first end is arranged to define the closed end, preferably, the receptacle includes no seams between said first and second ends. Said receptacle is preferably formed from lay-flat tubing. It is preferably sealed at said first end as described and is divergent (e.g. by being splayed) at said second end.

Said elongate housing is preferably arranged to support the receptacle which is suitably arranged within the housing.

Said elongate housing preferably includes cooling means for cooling reagents and polymer contained in the receptacle in use. Said cooling means may comprise a cooling and/or refrigeration device which is arranged to remove heat from the receptacle. Further details are provided hereinafter. It should be appreciated, however, that if is desired in any case to heat the receptacle, the cooling means described may be modified to circulate a heating fluid rather than a coolant fluid.

Said elongate housing preferably includes inerting means for introducing and/or maintaining an inert atmosphere in and/or around the receptacle.

Said elongate housing preferably comprises a first elongate tube in which said receptacle is positioned. In use (e.g. when inflated and/or when containing reagents for preparation of a polymer as herein described), said receptacle preferably contacts an internal surface of the first elongate tube. At least 60%, at least 75%, or at least 90% of the area of an external wall area of said receptacle preferably contacts said internal surface. Said receptacle preferably has a substantially circular cross-section, for example along at least 50%, at least 75%, at least 90% or at least 95% of its length. The area of the cross-section of the receptacle may be substantially constant, for example along at least 50%, at least 75%, at least 90% or at least 95% of its length.

Preferably, said first elongate tube has a circular cross-section and said receptacle can be arranged to have a circular cross-section. The ratio of the maximum diameter of the receptacle divided by the diameter of the first elongate tube, suitably in a region wherein the first elongate tube and receptacle are opposite one another, may be at least 0.8, preferably at least 0.9, more preferably at least 0.95. Said ratio may be 1.2 or less, preferably less than 1.1, more preferably less than 1.05. Suitably the aforementioned ratios apply along at least 50% or at least 80% of the length of the receptacle. Thus, in a preferred embodiment, the ratio of the maximum diameter of the receptacle (measured at any position along at least 50% or at least 80% of the length of the receptacle) divided by the diameter of the first elongate tube at a position opposite the position at which the diameter of the receptacle is measured, is in the range 0.8 to 1.2, preferably in the range 0.95 to 1.1.

Said internal surface of said first elongate tube is preferably a substantially smooth surface; and/or preferably includes a relatively low coefficient of friction to enable the receptacle to slide over the internal surface, when urged to do so. Said internal surface is preferably uninterrupted across the majority (e.g. greater than 80% or greater than 90%) of its area. Said internal surface is preferably cylindrical, preferably circularly cylindrical. Said internal surface preferably has a constant cross-section along substantially its entire extent.

Said first elongate tube is preferably cylindrical, for example circularly cylindrical.

Said first elongate tube is preferably rigid and/or self-supporting. It may be made of a metal, for example steel.

Said first elongate tube may include a port (A) through a wall thereof to allow fluid to pass into and/or out of the first elongate tube in use. Said elongate tube may include one or a plurality of such ports.

Said elongate housing preferably comprises a second elongate tube which is suitably coaxial with said first elongate tube and said first elongate tube is suitably positioned within the second elongate tube. Said first and second elongate tubes are preferably radially spaced apart so an annular gap is defined between the first and second elongate tubes, there suitably being spacer means to maintain the gap. Said annular gap preferably defines a fluid passage for a coolant fluid.

The annular gap preferably extends around the first elongate tube so that coolant fluid suitably contacts at least 20%, at least 50%, at least 70%, at least 80%, or at least 90% of the surface area of said first elongate tube thereby to cool the first elongate tube (and consequently the receptacle therewithin). Especially, substantially the entirety of the surface area of first elongate tube is contacted in use by coolant fluid. Thus, the arrangement may define part of a or said cooling means for cooling reagents in the receptacle in use. The cooling means is suitably arranged to remove heat generated by the polymerisation occurring within the receptacle, due to the physical and thermal contact between the external surface of the receptacle and the internal surface of the first elongate tube.

Said second elongate tube is preferably cylindrical, for example circularly cylindrical.

Said second elongate tube is preferably rigid and/or self-supporting. It may be made of a metal, for example steel.

Said second elongate tube may include one or, preferably, a plurality of ports (e.g. a port (B) and a port (C)) through a wall of the second elongate tube to allow fluid to pass into and out of the second elongate tube (and suitably into and/or out of said annular gap), in use.

Said first elongate tube is preferably closed at a first end (which is suitably adjacent the first end of the receptacle) by a first end member. The first end member may include a port (e.g. port (D)) which extends therethrough to allow fluid to pass into and out of the elongate housing. Said first end member may include one or a plurality of such ports.

Said elongate housing preferably includes securement means for releasably securing the receptacle in position, within the first elongate tube as described. Thus, the housing is preferably arranged for removal of the elongate receptacle therefrom suitably after a polymer has been produced therein. In a preferred embodiment where the housing includes a first elongate tube as described, the housing and/or first elongate tube may be arranged for the receptacle to slide out of the first elongate tube and thereby be removed and/or disengaged therefrom.

Said securement means may comprise a clamp for clamping the receptacle in position. When the receptacle includes a second end (which is suitably splayed as described), the securement means may clamp the second end and/or regions adjacent thereto in position. Said clamp may include a second end plate which is suitably arranged to be operatively connected to the first elongate tube (when provided) of the elongate housing.

Said second end plate may include one or a plurality of ports (e.g. ports (E) and (F)) which extend therethrough to allow fluid to pass into and/or out of the elongate housing and/or said receptacle, in use.

When said apparatus includes cooling means as described, said apparatus may include a container (C1) for containing a coolant fluid, wherein the apparatus is arranged for delivery of coolant fluid from the container (C1) to a region outside said receptacle. When the apparatus includes first and second elongate tubes and an annular gap as described, said apparatus is preferably arranged (e.g. by including a pump) to deliver coolant fluid from receptacle (C1) into said annular gap. Coolant fluid may be circulated in use. In the event it is desired to heat reagents in the receptacle, as an alternative, a heating fluid (eg having a temperature above ambient temperature) may be used instead of said coolant fluid. In some cases, at one time during a polymerisation reaction using the apparatus a coolant fluid may be supplied and, at another time, a heating fluid may be supplied.

As an alternative to provision of said second elongate tube which cooperates with said first elongate tube to define an annular gap for circulation of coolant fluid as described, an alternative cooling device may be used. This may comprise a cooling assembly including an elongate (eg substantially rectangular cross-section) tube which is arranged to be secured (for example releasably secured) adjacent an outside surface of the first elongate tube. The cross-section is suitably configured so that a face thereof can make intimate thermal contact (eg face to face contact) with the first elongate tube. Coolant fluid may be circulated in use through the rectangular cross-section tube thereby to cool the first elongate tube and, consequently, the receptacle in thermal contact therewith.

In one embodiment, said container (C1) contains coolant fluid for cooling reagents and/or polymer in the receptacle in use. Said container (C1) is preferably operatively arranged, suitably via a pipe, to deliver coolant fluid into said annular gap.

Said apparatus may include a container (C2) for containing a monomer, wherein the apparatus is arranged for delivery of monomer into the receptacle. In one embodiment, said container (C2) contains monomer for delivery into the receptacle. Said container (C2) is preferably operatively arranged, suitably via a pipe, to deliver monomer into said receptacle.

Said apparatus may include a container (C3) for containing a catalyst, wherein the apparatus is arranged for delivery of catalyst into the receptacle. In one embodiment, said container (C3) contains catalyst for delivery into the receptacle. Said container (C3) is preferably operatively arranged, suitably via a pipe, to deliver catalyst into said receptacle.

Containers (C2) and (C3) may be arranged to deliver the monomer and catalyst respectively to a mixing region where they are contacted and mixed, wherein the mixing region is upstream of said receptacle. A pipe suitably is operatively arranged to deliver a mixture comprising monomer and catalyst from said mixing region into said receptacle.

The apparatus may include a mixing device for mixing monomer and catalyst and, preferably, said mixing device is provided upstream of said receptacle.

Said apparatus may include a container (C4) for containing an inert fluid (e.g. an inert gas such as nitrogen), wherein the apparatus is arranged to deliver the inert fluid into the apparatus and/or into the receptacle for inerting the apparatus and/or receptacle. In one embodiment, said container (C4) contains inert fluid. Said container (C4) is preferably operatively arranged, suitably via a pipe, to deliver inert fluid for inerting the apparatus and/or receptacle.

According to a second aspect of the invention, there is provided a method of producing a drag reducing polymer, the method comprising:

-   (i) selecting an apparatus according to the first aspect; -   (ii) introducing reagents (e.g. at least one monomer and at least     one catalyst) for preparation of said polymer into said receptacle     of said apparatus; -   (iii) controlling conditions around said receptacle for controlling     the polymerisation of said reagents therewithin.

Step (iii) may include operating a said cooling means as described according to the first aspect to cool the reagents and/or polymer in the receptacle during polymerisation.

Step (iii) may include introducing an inert fluid, for example inert gas, into the apparatus at or adjacent the receptacle for inerting the receptacle and/or a region around the receptacle.

The total weight of reagents introduced into said receptacle may be at least 12 g, is suitably at least 1000 g, is preferably at least 10000 g, is more preferably at least 20000 g and, especially, is at least 30000 g. The total weight may be less than 3300 kg, suitably less than 1000 kg, preferably less than 500 kg, more preferably less than 250 kg, especially less than 100 kg. The total weight of reagents introduced into said receptacle may be between 1000 g and 250 kg, preferably between 10000 g and 100 kg.

The polymer produced in the method may be any conventional or known polymeric drag reducing agent (DRA) including, but not limited to, poly(alpha-olefin), polychloroprene, vinyl acetate polymers and copolymers, poly(alkylene oxide) (PAO), and mixtures thereof and the like. In one embodiment, the monomer may be any monomer which, when polymerized, forms a polymer suitable for use as a drag reducing agent (DRA). Said at least one monomer may comprise an alpha-olefin. Preferred alpha-olefins may have a carbon chain length in the range 2 to 40 carbon atoms, preferably 4 to 25, more preferably 6 to 12 carbon atoms. Said at least one monomer may be selected from the group comprising: 1-hexene, 1-heptene, 1-nonene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, isobutylene; alkyl acrylates; alkyl methacrylates; styrene and alkyl styrene. Copolymers (which may include two or more dissimilar monomers) of these monomers may also make suitable drag reducing agents. Preferred monomers include alpha-olefins with a carbon chain length in the range 4 to 25, more preferably 6 to 12 carbon atoms. Preferred monomers are selected from the group comprising: 1-hexene, 1-heptene, 1-nonene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, isobutylene. An especially preferred monomer is 1-decene.

Preferred copolymer drag reducing agents may comprise repeat units derived from 1-decene, optionally (but preferably) in combination with repeat units from one or more further monomers. Such further monomers may be selected from 1-hexene, 1-octene and 1-dodecene, for example in a molar ratio of 1:9 to 9:1. An especially preferred copolymer drag reducing agent may be prepared from a monomer mixture comprising 1-hexene and 1-decene.

Any known suitable catalyst and/or co-catalyst may be used in the method as long as they sufficiently catalyse the reaction to a sufficient extent. Metallocenes are useful catalysts for polymerizing some monomers. In the case of alpha-olefins, polymerization may be conducted by the inclusion of a mixture of Ziegler-Natta catalyst and co-catalyst(s) into the monomer. Catalysts for the polymerization of alpha-olefins include, but are not necessarily limited to, powdered catalyst TiCl₃.AA (aluminum activated titanium trichloride); co-catalyst(s), diethylaluminum chloride (DEAC), and diethylaluminum ethoxide (DEALE); TEAL (triethyl aluminum chloride), tri-methyl aluminum, tri-isobutyl aluminum, MAO (methylaluminoxane), haloalkanes (e.g. 1, 2-dichlorethane) and the like. Of course, it will be necessary to match the co-catalyst with the main catalyst, so that the catalytic activity of the main catalyst is triggered only by the presence of a particular co-catalyst or class thereof.

The method may comprise, after step (ii), closing off access to (e.g. sealing) the receptacle, except, optionally, for an inlet via which inert fluid, for example an inert gas such as nitrogen, is introduced into the receptacle, for example at a relatively low pressure (e.g. of about 0.5 psi). After step (ii), a polymerisation reaction may be undertaken for a time of at least 10 hours, at least 1 day, at least 2 days, at least 3 days, at least 4 days or at least 5 days. It is preferably undertaken for less than 20 days. After a selected time, polymer may be removed from the apparatus. This may comprise removal of said receptacle containing polymer from the apparatus. Preferably, the receptacle is slid out of the housing. For example, when the housing includes a first elongate tube as described, said receptacle is slid over an internal surface of said first elongate tube, thereby to remove it from said first elongate tube, suitably so that said receptacle is fully disengaged from all other parts of the apparatus.

Said method is preferably a batch process for example for producing 12 g to 3300 kg, preferably 20 kg to 100 kg, more preferably 30 kg to 50 kg of polymer in said receptacle.

The method may include a step of removing polymer from said receptacle. Said method may comprise disengaging, for example peeling, the film of the receptacle from the polymer. Advantageously, this may be achieved without leaving any film derived from the receptacle on the polymer. Thus, in a preferred embodiment, at least 95 wt %, preferably at least 99 wt %, more preferably 100 wt % of the film of the receptacle is disengaged from the polymer. Thus, the polymer may be isolated from the receptacle and, therefore, preferably includes less than 1 wt %, more preferably less than 0.1 wt %, especially substantially 0 wt % of film derived from said receptacle.

The method may include the step of comminuting the polymer so as to define a particulate material.

The method may comprise producing a drag reducing formulation comprising comminuted polymer and a carrier therefor.

According to a third aspect, there is provided a drag reducing formulation prepared as described according to the second aspect.

According to a fourth aspect, there is provided a method of drag reduction comprising use of a drag reducing formulation according to the third aspect. The method may comprise contacting the drag reducing formulation with a liquid hydrocarbon which is arranged to flow through a hydrocarbon transportation pipeline.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention described herein mutatis mutandis.

Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a schematic representation of apparatus for producing a polymer

FIGS. 2(a) to 2(d) illustrate, in schematic cross-section, steps involved in producing a plastic reaction tube of the apparatus;

FIGS. 3(a) to 3(d) illustrate steps involved in assembling the apparatus, including the plastic reaction tube;

FIGS. 4(a) and 4(b) illustrate steps involved in readying the assembled apparatus of FIG. 3(d) for use in a polymerisation process;

FIG. 5 illustrates the apparatus being charged for bulk polymerisation;

FIGS. 6 and 7 show steps in the removal of the plastic reaction tube from other parts of the apparatus; and

FIG. 8 shows a sealed tube containing polymer;

FIG. 9 shows a log of polymer removed from the reaction tube;

FIG. 10(a) is a representation of the apparatus of FIG. 1, but additionally including a thermocouple for monitoring temperature during the polymerisation process;

FIG. 10(b) is a representation of the thermocouple in side elevation;

FIG. 10(c) is an end view in the direction of arrow X(c) of FIG. 10(b); and

FIG. 11 is a schematic diagram of a simplified apparatus for producing a polymer.

In the Figures, the same or similar parts are annotated with the same reference numerals.

Referring to FIG. 1, apparatus 2 for carrying out a polymerisation reaction to produce, for example, a DRA involving monomer(s) and catalyst comprises a rigid elongate support tube assembly 4 which includes a coolant containing cooling jacket 6. The jacket 6 includes a coolant inlet 8 and a coolant outlet 10. Within the supporting tube assembly 4 is arranged an inflatable plastic reaction tube 12 (shown in a substantially filled state in FIG. 1) which abuts an internal wall 14 of the support tube assembly 4. End fitting 16 at one end of support tube assembly 4 includes a fluid port 18 via which an inert gas may exit the apparatus. End fitting 20 at an opposite end of support tube assembly 4 includes fluid ports 22, 24 in which fluids (e.g. monomer(s) and/or catalyst(s) and/or inert gas) may be introduced and/or removed from the apparatus during operation. In use of the apparatus, polymer is produced within the plastic reaction tube 12 while the tube 12 is cooled by contact with internal wall 14 of support assembly 4 which is cooled by coolant passing within cooling jacket 6 and while a positive pressure of inert gas is maintained around the tube 12. The contents of the plastic reaction tube may be maintained under inert gas conditions, through the application of inert gas via ports 22 and/or 24 while the polymerisation process is carried out. After completion of the polymerisation, end fitting 20 is removed and the plastic reaction tube 12 containing polymer produced is withdrawn from the assembly 4. The reaction tube 12 (i.e. the plastic material of which it consists) is disengaged, for example peeled, from the polymer to isolate the polymer from the reaction tube. The polymer may then be comminuted and formulated for use as a drag reducing additive.

Features of the apparatus and associated processes are described in greater detail below.

FIGS. 2(a) to (d) illustrate steps involved in producing the inflatable plastic reaction tube 12 which, in its finished state, is as represented in FIG. 2(d).

The reaction tube 12 is formed from 125 μm (500 gauge) lay flat, polyethylene tube 26 which is initially not closed at either end The tube has a length of about 600 cm plus an additional 5 cm to 10 cm (to enable it to be clamped in position as described hereinafter) and a width of about 153 mm±5 mm when in its flattened state shown in FIG. 2(a).

In a first step, shown in FIG. 2(b), one end of the tube is heat sealed as represented by number 28, thereby to fully close off the end and define one closed end of a receptacle for a polymerisable mixture.

In a second step, shown in FIG. 2(c), open end of the tube 26 (opposite the closed end) is stretched (as illustrated by reference numeral 27) over a heated cone 30 thereby to splay the tube in a region thereof towards its open end. As a result, the diameter of the tube 26 adjacent its open end gradually increases on moving from region 32, inwards of the open end, to region 34, situated at said open end.

In a third step, shown in FIG. 2(d), the cone 30 and tube 26 are disengaged thereby to leave splayed open end 35 which has been permanently deformed by the heat treatment using the heated cone 30.

The open end is splayed as aforesaid to facilitate securement of the open end within the apparatus in such a way as to minimise air gaps between the plastic reaction tube 12 and associated fittings of the apparatus. If air was to become trapped within folds of the plastic reaction tube 12, such air could be detrimental to the polymerisation process and/or reagents used therein. In addition, the splaying facilitates production of a fluid-tight seal between the plastic tube and fittings of the apparatus.

The apparatus 2 may be assembled as described with reference to FIGS. 3(a) to 3(d).

Referring to FIG. 3(a), support tube assembly 4 includes an inner rigid tube 38 arranged within an outer rigid tube 40. Spacers (not shown) are provided between tubes 38, 40 to maintain spacing therebetween thereby to define a passageway 42 between the tubes 38, 40 in which cooling fluid can flow. Ends of the outer rigid tube are welded to the outer surface of the inner rigid tube, to close the ends of the jacket assembly. Coolant inlet 8 communicates with the passageway 42 for passage of cooling fluid from the outside into the passageway 42 via the inlet 8 and out thereof via outlet 10. The cooling fluid can flow within the passageway around substantially the entirety of tube 38, before it exits the passageway via coolant outlet 10. Thus, a cooled, jacketed support tube assembly is arranged around the plastic reaction tube 12.

Inner tube 38 may suitably be made from stainless steel (e.g. 55304L) of thickness 0.083″ (2.1 mm) and may have an outer diameter of 4″ (101.6 mm). The length may be 20 ft (609.6 cm). An inlet 13 (FIG. 1) is provided for introduction of gas into the inside of the inner tube 38 as described below.

Outer tube 40 may suitably be made from stainless steel (e.g. SS304L) of thickness 0.12″ (3 mm) and may have an inner diameter of 108 mm and an outer diameter of 4.5″ (114.3 mm). The length may be 19 ft 7½″ (598.2 cm).

Coolant inlet 8 and outlet 10 may be fabricated with a 0.5″ NPT Weldolet (Trade Mark). A push fit adaptor may be used to allow easy connection or removal of tubing for coolant.

End fitting 16 may comprise a suitable gasket and a sanitary stainless steel end plate with a single tapped thread for the port 18.

At the left hand end of FIG. 3(a), there is shown a 4″ (101.6 mm) Viton (Trade Mark) tri-clamp gasket 44 and an end plate 46. The end plate 46 incorporates inlets/outlets 22, 24 which may be tapped into the end plate. A push fit adaptor may be provided allowing convenient connection and removal of polyethylene (PE) tubing. Inlet/outlet 24 incorporates a ½″ NPT ball valve. As described hereinafter, during the process described inlet/outlet 24 is used in three different steps—(a) inflation and inert gas flushing of the reaction tube 12; (b) charging of monomer/catalyst mixture; and (c) flushing with inert gas after charging with the monomer/catalyst mixture (to clear delivery lines and provide additional inertion of the apparatus contents).

Also as described hereinafter, during the process described inlet/outlet 22 may be used as an inert gas outlet during inflation of reaction tube 12, inerting and monomer/catalyst charging; and subsequently as an inlet for inert gas (to maintain a small positive pressure inside the reaction tube 12 for the remainder of the bulk polymerisation process).

Although in the figures the apparatus is shown with the elongate axes of tubes 38, 40 of the support tube assembly 4 horizontal, it is preferred that the tubes are raised at the left hand end of FIGS. 3(a) to (d) to facilitate flow of fluids from their position of introduction and into the reaction tube 12 defined by tube 26; and to avoid loss of monomer/catalyst via port 22 during charging. Typically the angle defined by tubes 38, 40 to the horizontal is about 2 to 3° (or the gradient is about 1 in 20).

The reaction tube 12, produced from tube 26 as described in FIG. 2(d), is inserted into the inner tube 38 and pushed thereinto so its heat sealed end 28 is adjacent end fitting 16. As shown in FIG. 3(b), initially the splayed open end 35 protrudes from the inner tube 38. Next, as shown in FIG. 3(c), the splayed open end 35 is turned back over flange 48 produced on inner tube 38. Then, as represented in FIG. 3(d), gasket 44 and end plate 46 are secured in position thereby firmly (and sealingly) clamping the open end 35 in position as represented in FIG. 3(d). Note in FIG. 3(d) sanitary fitting clamps have been omitted in the interests of clarity.

As will be noted from FIG. 3(d) after insertion of tube 12 (and prior to inflation thereof) the tube is flaccid as represented in FIG. 3(d).

After assembly of the apparatus as described with reference to FIGS. 3(a) to 3(d), the apparatus may be readied for use, as described with reference to FIGS. 4(a) and 4(b), by inflating the tube 12 and inerting any region of the apparatus which may contact monomer/catalyst subsequently introduced into the apparatus, including indirect contact occurring via gas diffusion through the tube.

Referring to FIG. 4(a), initially the volume within the apparatus outside the tube 12 and within the inner tube 38 is inerted to a specified level (e.g. less than 0.3% vol oxygen by introduction of inert gas (e.g. nitrogen) via port inlet 13 as represented by arrows in FIG. 4(a). The inert gas exits via port 18. The oxygen content of gas exiting the inner tube 38 may be monitored at a downstream sampling point (not shown) using standard methods.

Next, the tube 12 is inflated as shown in FIG. 4(b), using an inert gas (for example nitrogen). Inert gas is passed through the tube until the inert gas exiting via port 22 has an oxygen content (e.g. of less than 0.3% vol), measured at a downstream sampling point (not shown). Inflation involves introduction of the inert gas via port 24 into the tube 12.

The gas circulates within the tube 12 to inflate it and exits via port 22. During inflation of tube 12, inert gas supply via port 13 is stopped. Inflation of tube 12 can be verified by observing gas flow from port 18, resulting from displacement of a gas volume from outside tube 12 due to inflation of the tube 12. Once inflation of the tube 12 has been completed as shown in FIG. 4(b), port 18 is temporarily closed off, while inerting of tube 12 is completed, to prevent air ingress via port 18. Port 18 is reopened prior to charging of monomer(s)/catalyst(s) to the apparatus.

As an alternative to the sequence of steps described with reference to FIGS. 4(a) and 4(b), the sequence of steps may be interchanged—e.g. the tube 12 may be inflated first and then sealed before inerting the region outside tube 12. Alternatively, the steps of FIGS. 4(a) and 4(b) could be undertaken substantially simultaneously, with a slightly higher gas pressure within tube 12 to keep it in an inflated condition.

After completion of step 4(b), the apparatus is ready to be charged with reagents and polymerisation undertaken. Referring to FIG. 5, the flow of coolant in the passageway 42 between tubes 38, 40 is progressed by introducing coolant thereinto via inlet 8 and removing coolant therefrom via outlet 10. Next, a monomer/catalyst mixture is introduced into the inflated tube 12 via port 24 thereby to fill tube 12. The polymerisation reaction is then allowed to proceed for an appropriate length of time (typically about 6 days). During this time, coolant is flowed continuously and temperature may be monitored. For example, some apparatus may include a suitably positioned thermocouple 91 (FIG. 10). In addition, a relatively low pressure (approx. 0.5 psi) of inert gas is applied via ports 22 and 13 to ensure the tube 12 (and its polymerising contents) is maintained under an inert atmosphere.

The monomer(s)/catalyst(s) mixture is suitably arranged to produce an ultra-high molecular weight polymer for use in drag reduction. The polymer may suitably be a polymer and/or copolymer of alpha-olefin(s).

Using the apparatus, polymer was prepared from 1-decene monomer, as described in Example 1.

Example 1—Production of Polymer

1-decene monomer (31.6 kg) was purged with nitrogen for 60 minutes to remove dissolved oxygen which would otherwise be poisonous to the catalyst used. The monomer was passed through a pre-treatment column containing 1.5 kg of a 50:50 mixture of 13X and 5A molecular sieves (which had been pre-dried under vacuum at high temperature). Post the pre-treatment column, the monomer was pumped to a 90 litres stirred and jacketed glass lined reactor which had previously been dried and inerted to 0.3 vol % oxygen or lower.

The 1-decene was cooled to 5° C. and then 25 wt % diethylaluminium chloride (DEAC) (80.45 g) in heptane was transferred to a Swagelok (Trade Mark) bomb within a glove box. This was then added to the 1-decene under an inert atmosphere to scavenge any residual water or protic impurities. The mixture was then stirred for 20-30 minutes in a 90 litres reactor.

Inside a glovebox, titanium trichloride aluminium activated TiCl₃(AAD) (3.7888 g), was dispersed with stirring into anhydrous heptane (157.6 ml), anhydrous 1,2-dichloroethane (1.37 ml) and isobutylaluminoxane (IBAO) in heptane (3.5 wt % aluminium content in heptane) (41.4 ml) was added to the catalyst dispersion. The mixture was stirred, then transferred to a Swagelok bomb and subsequently transferred to the 90 litres reactor, whilst maintaining an inert atmosphere, to initiate the Ziegler Natta polymerisation.

It is found that, on mixing of monomer and catalyst, polymerisation is instantly initiated and thus proceeds rapidly. The mixture was then rapidly introduced using inert gas pressure to the inflated tube 12 via port 24 as described above with reference to FIG. 5.

The reaction mixture was held within tube 12, as shown in FIG. 5, at a jacket temperature of 5° C. Chilled water was flowed in passageway 42. After 24 hours, the temperature of fluid in passageway 42 was increased and the reaction continued.

During the entire process, both the outside and inside of tube 12 were kept under approximately 0.5 psi nitrogen pressure by introducing nitrogen via ports 13 and 22 to assist in restricting oxygen ingress into the polymerising mixture.

At the end of the aforementioned 6 days reaction time, gasket 44 and end plate 46 were disengaged as shown in FIG. 6, to provide access to the tube 12 which contained polymer 50. End plate 16 may optionally also be removed to allow visual inspection of polymer in the tube 12. The tube 12 (and polymer) were then manually withdrawn from inner tube 38, as shown in FIG. 7. During the withdrawal, the open end of tube 26 was closed by a tightly drawn cable tie 52 (or the like). Subsequently, the tube was fully removed to isolate the sealed tube 12 containing an approximately 20 feet (610 cm) log of polymer 50 as shown in FIG. 8.

The tube 12 (which is made from polyethylene as described) can readily be detached, for example cut and/or peeled away from the log of polymer 50, to thereby produce an isolated log 50 of polymer, as a single piece, as shown in FIG. 9. Substantially no PE residue contaminates the polymer after removal of tube 12 which may minimise contamination of the polymer, and in turn, may be advantageous in downstream uses thereof. Whilst not wishing to be bound by any theory, the ease with which the tube can be cut away from polymer 50 may be related to the fact the polymer has a higher bulk density (approximately 0.85 g/cm³) than the 1-decene (density 0.74 g/cm³) starting material which means the polymer tends to shrink away from the wall of the receptacle as it is formed.

The log of polymer 50 of FIG. 9 may be processed, by known methods and contacted with a carrier to produce a formulation comprising a DRA.

Other procedures undertaken are described in Examples 2 to 7. Examples 2 to 6 describe procedures for assessing characteristics of polymers produced as described herein and results of such assessments.

Example 2—Determination of Polymer Conversion Percentage in a Polymer Produced

A disposable aluminium dish was weighed to four decimal places and the weight recorded (A). A sample of the test material (2-3 g) was placed in the dish and the combined weight of the dish and sample also weighed to four decimal places (B). The sample was dried in a vacuum oven (200° C., 0.04 Torr) for one hour, removed and reweighed. This process was repeated until constant weight (C) was achieved.

The polymer conversion percentage was calculated as follows:

% conversion=(C−A)/((B−A)*D)

where D is equivalent to the percentage purity of the commercial alpha-olefin monomer used/100. For example, D=0.994 for commercial 1-decene of purity 99.4%.

Example 3—Determination of Percentage Drag Reduction of Polymer Produced

Step 1—Preparation of Working Solution

n-Hexane (˜80 mL) was charged to a 250 mL bottle. A piece of the test polymer was sampled directly from the polymer log, as prepared in the bulk polymerisation reaction and accurately weighed to four decimal places (0.0150-0.0200 g). The polymer was then dissolved in the n-hexane by mixing for 2 days under low shear conditions, to provide a solution (A).

Solution (A) was then transferred to a clean, preweighed 500 mL bottle and accurately topped up with further n-hexane to provide a final polymer concentration of 100 mg/kg (100 ppm w/w). The sample was manually mixed, avoiding vigorous shaking, providing partially diluted solution (B).

An aliquot of solution (B) (4 g) was accurately weighed into a clean, preweighed 1000 mL bottle, then accurately topped up with further n-hexane to the target sample weight (400 g). The sample was manually mixed as above to provide working solution (C) 1 mg/kg (1 ppm w/w).

Step 2—Drag Reduction Testing Procedure

Clean, preweighed collection bottles (1000 mL) were used for collection of liquids during the test runs.

The test apparatus consisted of a 2 litre pressure vessel, fitted with charging inlet for solvent, bottom run off (used for cleaning purposes at the end of experiments), and a dip leg connected to a length of stainless steel tubing external to the vessel (7 feet length, 6.35 mm OD, 0.89 mm wall thickness). The tubing was fitted with a control valve at the outlet. The pressure vessel was further fitted with an inert gas inlet, connected to a supply line via a precision pressure control valve. This was set at a constant pressure (2.6 psi) for all experiments.

The vessel was charged with ˜400 g of either working solution (C) as prepared in Step 1, or untreated n-hexane (control sample), then sealed and pressurised with inert gas (2.6 psi) with the outlet control valve closed. This valve was then opened allowing liquid to purge the external tubing, then closed (this liquid was discarded). A preweighed collection bottle (1000 mL) was placed at the outlet, then the valve reopened for 12-13 seconds to allow the liquid to flow again, recording the elapsed time using a stopwatch. The remaining liquid in the vessel was then discarded, rinsing the vessel thoroughly with untreated n-hexane (for test cycles where solution (C) was used).

The percentage flow improvement (% FI) and percentage drag reduction (% DR) were calculated from the hexane blank flow rate (F0) and the treated sample (solution (C)) flow rate (Fa) as follows:

F0 in g/sec=(collected weight in g)/(time valve was opened in seconds)

Fa in g/sec=(collected weight in g)/(time valve was opened in seconds)

then

% FI=100*(Fa−F0)/F0

% DR=[(1+% FI)^(1.9)−1]/(1+% FI)^(1.9)

Examples 4 to 6-Production of Polymers Using Different Catalyst Amounts

Three separate bulk polymerisation reactions (Examples 4 to 6 respectively) were carried out using the apparatus described above, with 1-decene as the monomer. The synthesis procedure was identical to that described in Example 1 other than modification of the charges of TiCl₃(AAD), 1,2-dichloroethane, isobutylaluminoxane solution and heptane diluent, to provide different levels of catalyst loading (expressed as ppm w/w of Ti relative to the monomer charge weight). After completion of the bulk polymerisation the reaction tube comprising the polymer was removed according to the procedure above, and the polymer sampled for analysis, as described in Examples 2 and 3.

For each of the polymer products, polymer conversion percentages were determined for 10 samples, taken from different points within the polymer log. These points were selected to provide information on the consistency of polymerisation along both the long axis and the cross sectional diameter of the polymer log.

For each of the polymer products, percentage drag reduction (% DR) was determined as described in Example 3 for four samples taken from different points within the polymer log. These points were selected to provide information on the consistency of product performance characteristics along the long axis of the polymer log.

The results of these experiments are shown in Table 1.

TABLE 1 Ex- % polymer conversion % drag reduction ample Catalyst Standard Standard No. (ppm w/w Ti) Average deviation Average deviation 4 120 87 1 50.49 1.61 5 100 87 1 49.60 0.81 6  80 83 1 51.62 0.68

The results show that, when bulk polymerisations were carried out using the apparatus described, products with excellent performance characteristics were obtained. The data shows that polymerisation could be successfully achieved using the apparatus, across a range of catalyst concentrations typical for this application. Furthermore, for each individual experiment the data showed excellent consistency in both chemical composition and performance characteristics, throughout the polymerised reaction volume.

Examples 7 to 9—Production of Copolymers

Three separate bulk polymerisation reactions (Examples 7 to 9 respectively) were carried out using the apparatus described above, with a monomer mixture of 1-hexene and 1-decene. The synthesis procedure was identical to that described in Example 1 (120 ppm w/w of Ti relative to the monomer charge weight) other than the selection of monomers. After completion of the bulk polymerisation the reaction tube 12 comprising the polymer was removed according to the procedure above, and the polymer sampled for analysis, as described in Examples 2 and 3.

Polymer conversion percentages and percentage drag reduction (% DR) measurements, from multiple points within the polymer log, were taken and reported in identical manner to Examples 4 to 6.

The results of these experiments are shown in Table 2.

TABLE 2 1-hexene 1-decene % polymer conversion % drag reduction Example mol mol No. wt % % wt % % Average Standard deviation Average Standard deviation 7 60.0 71.4 40.0 28.6 87 1 51.92 0.67 8 35.7 48.0 64.3 52.0 88 3 50.90 0.68 9 28.6 40.0 71.4 60.0 89 3 51.66 0.35

The results show that, when bulk polymerisations were carried out using the apparatus described to make copolymers, products with excellent performance characteristics were also obtained. Similarly to Examples 4 to 6, the data showed excellent consistency in both chemical composition and performance characteristics, throughout the polymerised reaction volume.

An alternative, simplified, apparatus 110 is shown in FIG. 11. The apparatus 110 for undertaking a chemical reaction comprises an elongate housing 112 and a receptacle 114. The elongate housing 112 includes a cooling means 116 and end fittings 118, 120 which include ports via which fluids may be introduced and/or removed. In use of the apparatus 110, a chemical reaction product is formed within the receptacle 114. Subsequently, the receptacle 114 containing the chemical reaction product is withdrawn from the elongate housing 112.

Although only one apparatus 2, 110 has been described, an assembly may be provided including multiple apparatuses 2, 110 to manufacture larger amounts of polymer. Such reactors could be filled sequentially or simultaneously, optionally through the use of a manifold system.

In another embodiment, shown in FIG. 11, apparatus for carrying out a polymerisation reaction may comprise multiple assemblies, each comprising a reaction tube 2 within a rigid tube 38. The assemblies may collectively be surrounded by a single cooling jacket which is arranged to cool all of the reaction tubes concurrently. For example, two or more assemblies, each comprising a reaction tube 2 within a rigid tube 38, may be axially aligned and a single cooling jacket may envelope the tubes. In an alternative, a plurality of assemblies, each comprising a reaction tube 2 within a rigid tube 38, may be in a stacked arrangement, with a single cooling means being arranged to cool the plurality.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 

1-27. (canceled)
 28. An Apparatus for undertaking a polymerisation reaction to produce a drag reducing polymer, the apparatus comprising: (a) an elongate housing; and (b) an elongate receptacle within the housing, said receptacle being arranged to receive reagents for reaction in the apparatus to produce a drag reducing polymer.
 29. The apparatus according to claim 28, wherein said receptacle comprises a plastic film material which has a thickness of at least 20 μm (preferably at least 50 μm) and a thickness of less than 2000 μm (preferably less than 1000 μm); and/or wherein the internal wall area of the receptacle is defined as the area of the receptacle which is arranged to contain material (e.g. polymer in use), wherein at least 50% (preferably about 100%) of the internal wall area is defined by a said plastic film material which consists of a single layer.
 30. The apparatus according to claim 29, wherein said plastic material of said film comprises an optionally-substituted polyolefin polymer, for example polyethylene.
 31. The apparatus according to claim 29, wherein said receptacle includes a first end and a second end which are spaced apart along the elongate extent of the receptacle, wherein said first end is a closed end and includes a sealed region, wherein said receptacle is formed from lay-flat tubing.
 32. The apparatus according to claim 31, wherein the length of the receptacle is the linear distance between said first end and said second end, wherein the diameter of the receptacle is substantially constant for at least 80% (preferably at least 90% or 95%) of the length thereof; and wherein a region of the receptacle adjacent said second end diverges so an opening of the receptacle at said second end has a greater diameter than a region of the receptacle inwards of the second end.
 33. The apparatus according to claim 28, wherein the diameter of the receptacle is in the range lcm to 45 cm (and is preferably at least 7 cm and less than 30 cm) across its entire extent; and/or the length of the receptacle is in the range 15 cm to 60 m (and is preferably in the range 3 m to 15 m); and/or the volume of the receptacle is in the range 12 cm³ to 4 m³ (preferably in the range 4000 cm³ to 0.5 m³); and/or the aspect ratio of the elongate receptacle, defined as the length of the internal volume of the receptacle divided by the diameter of the internal volume of the receptacle, is at least 10 and less than 600, and wherein said aspect ratio is preferably between 30 and
 150. 34. The apparatus according to claim 33, wherein a ratio of the maximum diameter of the receptacle divided by the diameter of the housing, in a region wherein the housing and receptacle are opposite one another, is at least 0.8 and is 1.2 or less.
 35. The apparatus according to claim 28, wherein said elongate housing is arranged to support the receptacle which is arranged within the housing; wherein said elongate housing includes cooling means for cooling reagents and polymer contained in the receptacle in use; and wherein said elongate housing includes inerting means for introducing and/or maintaining an inert atmosphere in and/or around the receptacle.
 36. The apparatus according to claim 28, wherein said elongate housing comprises a first elongate tube in which said receptacle is positioned, wherein said receptacle contacts an internal surface of the first elongate tube, wherein at least 60% of the area of an external wall area of said receptacle contacts said internal surface, wherein, optionally, said first elongate tube has a circular cross-section and said receptacle can be arranged to have a circular cross-section, wherein an internal surface of said first elongate tube is uninterrupted across greater than 80% of its area; and/or said internal surface is cylindrical, and has a constant cross-section along substantially its entire extent.
 37. The apparatus according to claim 36, wherein said receptacle has a substantially circular cross-section in use, along at least 95% of its length; and/or the area of the cross-section of the receptacle in use is substantially constant, along at least 90%, of its length.
 38. The apparatus according to claim 37, wherein said elongate housing comprises a second elongate tube which is coaxial with said first elongate tube and said first elongate tube is positioned with the second elongate tube, said first and second elongate tubes being radially spaced apart so an annular gap is defined between the first and second elongate tubes, wherein said annular gap defines a fluid passage for a coolant fluid.
 39. The apparatus according to claim 38, wherein the annular gap extends around the first elongate tube so that coolant fluid can contact at least 70% of the first elongate tube in use thereby to cool the first elongate tube.
 40. The apparatus according to claim 39, wherein said first and second elongate tubes are cylindrical.
 41. The apparatus according to claim 36, wherein said elongate housing includes securement means for releasably securing the receptacle in position within the first elongate tube, wherein, optionally, the housing includes a first elongate tube and the housing and/or first elongate tube are arranged for the receptacle to slide out of the first elongate tube and thereby be removed and/or disengaged from the housing.
 42. The apparatus according to claim 28, wherein said apparatus includes a container (C1) for containing a coolant fluid, wherein the apparatus is arranged for delivery of coolant fluid from the container (C1) to a region outside said receptacle; and/or wherein said apparatus includes a container (C2) for containing a monomer, wherein the apparatus is arranged for delivery of monomer into the receptacle; and/or wherein said apparatus includes a container (C3) for containing a catalyst, wherein the apparatus is arranged for delivery of catalyst into the receptacle; and/or said apparatus includes a container (C4) for containing an inert fluid, wherein the apparatus is arranged to deliver the inert fluid into the receptacle for inerting the receptacle.
 43. The apparatus according to claim 42, wherein container (C2) contains monomer and container (C3) contains catalyst wherein containers (C2) and (C3) are arranged to deliver monomer and catalyst respectively to a mixing region wherein they are arranged to be contacted and mixed, wherein the mixing region is upstream of said receptacle.
 44. A method of producing a drag reducing polymer, the method comprising: (i) selecting an apparatus according to claim 1; (ii) introducing reagents comprising at least one monomer and at least one catalyst for preparation of said polymer into said receptacle of said apparatus; (iii) controlling conditions around said receptacle for controlling the polymerisation of said reagents therewithin.
 45. The method according to claim 44, wherein step (iii) includes operating a cooling means to cool the reagents and/or polymer in the receptacle during polymerisation; and/or step (iii) includes introducing an inert fluid into the apparatus at or adjacent the receptacle for inerting the receptacle and/or a region around the receptacle.
 46. The method according to claim 45, wherein after step (ii), a polymerisation reaction is undertaken for a time of at least 10 hours, preferably at least 1 day and subsequently said receptacle containing polymer is slid out of the housing.
 47. The method according to claim 46, wherein the method includes a step of removing polymer from said receptacle by disengaging the film of the receptacle from the polymer and the method comprises producing a drag reducing formulation comprising comminuted polymer and a carrier therefor.
 48. The apparatus according to claim 43, wherein container (C2) contains monomer selected from the group comprising: 1-hexene, 1-heptene, 1-nonene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, isobutylene; alkyl acrylates; alkyl methacrylates; styrene and alkyl styrene; and container (C3).
 49. The method according to claim 44, wherein said apparatus selected includes a container (C1) for containing a coolant fluid, wherein the apparatus is arranged for delivery of coolant fluid from the container (C1) to a region outside said receptacle; and/or wherein said apparatus includes a container (C2) containing a monomer, wherein the apparatus is arranged for delivery of monomer into the receptacle; and/or wherein said apparatus includes a container (C3) for containing a catalyst, wherein the apparatus is arranged for delivery of catalyst into the receptacle; and/or said apparatus includes a container (C4) for containing an inert fluid, wherein the apparatus is arranged to deliver the inert fluid into the receptacle for inerting the receptacle; wherein container (C2) contains monomer selected from the group comprising: 1-hexene, 1-heptene, 1-nonene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, isobutylene; alkyl acrylates; alkyl methacrylates; styrene and alkyl styrene; and container (C3).
 50. An apparatus for undertaking a polymerisation reaction to produce a drag reducing polymer, the apparatus comprising: (a) an elongate housing; (b) an elongate receptacle within the housing, said receptacle being arranged to receive reagents for reaction in the apparatus to produce a drag reducing polymer; wherein said receptacle comprises a plastic film material which has a thickness of at least 50 μm and a thickness of less than 1000 μm; wherein said receptacle includes a first end and a second end which are spaced apart along the elongate extent of the receptacle, wherein said first end is a closed end; wherein the diameter of the receptacle is substantially constant for at least 80% of the length thereof; wherein the diameter of the receptacle is in the range at least 7 cm and less than 30 cm across its entire extent; wherein the length of the receptacle is in the range 3 m to 15 m and/or the volume of the receptacle is in the range 12 cm³ to 4 m³′ wherein said elongate housing is arranged to support the receptacle which is arranged within the housing; wherein said elongate housing includes cooling means for cooling reagents and polymer contained in the receptacle in use; wherein said elongate housing includes inerting means for introducing and/or maintaining an inert atmosphere in and/or around the receptacle; wherein the housing includes a first elongate tube and the housing and/or first elongate tube are arranged for the receptacle to slide out of the first elongate tube and thereby be removed and/or disengaged from the housing. wherein said apparatus includes a container (C1) for containing a coolant fluid, wherein the apparatus is arranged for delivery of coolant fluid from the container (C1) to a region outside said receptacle; wherein said apparatus includes a container (C2) containing a monomer, wherein the apparatus is arranged for delivery of monomer into the receptacle; wherein said apparatus includes a container (C3) for containing a catalyst, wherein the apparatus is arranged for delivery of catalyst into the receptacle; wherein said apparatus includes a container (C4) for containing an inert fluid, wherein the apparatus is arranged to deliver the inert fluid into the receptacle for inerting the receptacle; wherein container (C2) contains monomer and container (C3) contains catalyst wherein containers (C2) and (C3) are arranged to deliver monomer and catalyst respectively to a mixing region wherein they are arranged to be contacted and mixed, wherein the mixing region is upstream of said receptacle; wherein container (C2) contains monomer selected from the group comprising: 1-hexene, 1-heptene, 1-nonene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, isobutylene; alkyl acrylates; alkyl methacrylates; styrene and alkyl styrene. 